Locking applied to successive running Signals to enforce the replacement
of one lever (arm or aspectAny valid visual indication of a Signal as displayed to the driver. More) before the lever controlling the SignalA visual display device which conveys instructions or provides prior warning of instructions regarding the driver’s authority to proceed. More in rearAlternative term for Approach To. More is
free to be pulled. This Locking is non-reciprocal and may be performed
electrically or mechanically.